1. Field of the Invention
The present invention relates to the improvement of a heat radiation structure of a resin sealed semiconductor device, and particularly, it relates to a heat radiation structure of a semiconductor device which can satisfy three conditions required for a heat radiation member, i.e., (1) heat conductivity being excellent, (2) a difference of a coefficient of linear expansion between the heat radiation member and a sealing resin being small, and (3) adhesive properties to the sealing resin being good.
2. Description of the Related Art
A pin grid array (PGA) and a ball grid array (BGA) have generally been known as semiconductor devices in which high-density mounting is possible. Each of the PGA and BGA is a semiconductor device which is manufactured by mounting an IC chip on a resin substrate having a plurality of contact electrodes on an underside, and then sealing the IC chip on the substrate with a resin.
Moreover, in recent years, this type of PGA and BGA has been commercialized by sealing the IC chip mounted on the substrate with the resin by injection molding, and then integrally forming a metallic radiation member on an upper surface of the sealing resin to enhance a heat radiation effect of the IC chip.
The semiconductor device including the metallic heat radiation member integrally formed with the sealing resin is shown in FIG. 7.
A semiconductor device 101 shown in the drawing has a structure in which an IC chip 103 is mounted on a circuit substrate 102 made of a resin, the IC chip 103 and a bonding wire 105 are resin-sealed with a sealing resin 106 by injection molding, and a metallic heat radiation member 107 is integrally formed with the sealing resin above the IC chip 103.
A plurality of pins 104 which function as external connection terminals are disposed on an underside of the circuit substrate 102.
In this semiconductor device, when the IC chip 103 mounted on the circuit substrate 102 is sealed by the resin, the resin substrate 102 with the IC chip 103 mounted thereon is held by a lower mold member of a molding mold, and the heat radiation member 107 is held by an upper mold member. In this state, an injection molding resin is injected through an injection port, whereby the metallic heat radiation member 107 can integrally be formed on the upper surface of the sealing resin 106.
However, as a result of subsequent intensive researches, the present applicant has found that, in the constitution in which the metallic heat radiation member is integrally formed on the upper surface of the sealing resin by injection molding, there must be considered the peeling of the sealing resin and the heat radiation member based on a difference of a coefficient of linear expansion between the injection molded resin and the heat radiation member.
That is, in the case that the difference of the coefficient of linear expansion between the injection molded resin and the heat radiation member is excessively large, and when the IC chip generates heat, a warp force is generated between the resin and the member, so that thermal peeling occurs sometimes between the sealing resin and the heat radiation member. Furthermore, considering conditions required for the heat radiation member including the occurrence of the thermal peeling, it has been found that the heat radiation member needs to satisfy three conditions, i.e., (1) the heat conductivity being excellent, (2) the difference of the coefficient of linear expansion between the heat radiation member and the sealing resin being small, and (3) adhesive properties to the sealing resin being good.
However, any single metal material cannot satisfy all the three conditions at a satisfactory level. In the actual situation, the heat radiation member is to be selected sacrificing any of the three conditions.
According to the present invention, there is provided a semiconductor device in which an IC chip mounted on a circuit substrate is sealed with a resin by injection molding, and a metallic heat radiation member is integrally formed on an upper surface of a sealing resin by the injection molding. The heat radiation member is constituted of a clad material in which different metals are combined.
Particularly, the heat radiation member is constituted of the clad material comprising a combination of a first metal having a coefficient of linear expansion close to that of the sealing resin, and a second metal having satisfactory adhesive properties to the sealing resin. Concretely, the first metal of the heat radiation member is preferably copper, and the second metal is aluminum.
Furthermore, the heat radiation member may comprise a three-layer structure in which the second metal is laminated on opposite surfaces of the first metal.
As described above, in the resin sealed semiconductor device of the present invention, the heat radiation member is constituted as the clad material in which the first metal having a coefficient of linear expansion close to that of the sealing resin is used as a core material, and the second metal having satisfactory adhesive properties to the sealing resin is laminated on the surfaces of the first metal.
Therefore, there can be obtained the metallic heat radiation member, which can satisfy three conditions required for the heat radiation member at a satisfactory level, i.e., (1) heat conductivity being excellent, (2) the difference of the coefficient of linear expansion between the heat radiation member and the sealing resin being small, and (3) adhesive properties to the sealing resin being good.
Moreover, according to the present invention, there can be provided the heat radiation member in which the first and second metals can arbitrarily be selected, and which is suitable for respective sealing resins different from one another in properties.
Furthermore, in the present invention, since the heat radiation member is constituted as the clad material, the heat radiation member having arbitrary properties can be obtained without increasing a processing cost.